Shuttle assembly for use in an injection molding machine

ABSTRACT

A shuttle assembly for an injection molding machine is provided. The shuttle assembly includes a shuttle-support unit adapted to be attached to the machine frame and a shuttle-mold interfacing unit, slidably coupled to the support unit. Mold-coupling members are provided for removably coupling a first movable mold platen unit and a second mold platen unit to the shuttle-mold interfacing unit. During operation of the shuttle assembly, a shuttle-drive unit selectively reciprocally indexes the shuttle-mold interfacing unit in a preferably horizontal shuttle-travel path between (i) a first shuttle position whereat the first movable mold platen unit, when coupled thereto, is situated at a first unloading/loading position, and the second movable platen unit, when coupled thereto, is situated at a clamping position; and (ii) a second shuttle position where the first movable mold platen unit, when coupled thereto, is situated at a clamping position, and the second movable platen unit, when coupled thereto, is situated at a second unloading position. In the preferred embodiment, the first unloading position and the second unloading position are located on opposite sides of the clamping position.

This is a division of application Ser. No. 07/774,448, filed Oct. 10,1991 now U.S. Pat. No. 5,209,889.

FIELD OF THE INVENTION

This invention relates to a shuttle assembly for use in an injectionmolding machine.

BACKGROUND OF THE INVENTION

The operational components of an injection molding machine usuallyinclude a stock supply assembly, an extruder assembly, an injectionassembly, a mold pallet assembly, and a clamping assembly. In a typicalmolding process, the stock supply assembly supplies a certain amount ofstock material to the extruder assembly. The extruder assemblyplasticizes the stock material into an injection material and conveys ameasured amount, or "shot", to the injection assembly. The injectionassembly then injects the material into a complete mold cavity formed bythe mold pallet assembly and the clamping assembly provides the forcenecessary for successful molding.

The mold pallet assembly is usually formed by two selectivelyjoinable/separable mold platen units. In most injection moldingmachines, at least one of the mold platen units is movable. When aninjection molding machine is used in an insert molding procedure, themold platen units are initially separated and an unfinished product isloaded into one of the mold platen units. The movable mold platen unitis then joined together with the stationary mold platen unit to form amold cavity. Once the mold cavity has been formed, the shot of injectionmaterial is then injected and the clamping assembly provides thenecessary force to hold the mold pallet assembly together. The movablemold platen unit is then separated from the stationary mold platen unitand the molded product is unloaded from the mold cavity.

In such a molding procedure, the injection molding machine is idle forsignificant periods of time because once the molding process has beencompleted, a subsequent molding process cannot begin untilloading/unloading steps are performed. Thus, the machine remains idleduring these loading/unloading steps.

SUMMARY OF THE INVENTION

The present invention provides an injection molding machine whicheliminates substantial periods of machine idleness. This is accomplishedby a shuttle assembly which allows the molding process to be performedon one mold platen unit while unloading/loading steps are performed onanother mold platen unit. The shuttle assembly also permits theunloading/loading steps to be efficiently and easily performed by anoperator of the machine. These features are believed to increaseproductivity by an average of 80% in insert molding procedures, and insome specific procedures to increase productivity as much as 400%.

More particularly, the present invention provides a shuttle assembly foran injection molding machine having a machine frame and a mold palletassembly which includes a first movable mold platen unit and a secondmovable mold platen unit. The shuttle assembly includes ashuttle-support unit which is adapted to be attached to the machineframe and a shuttle-mold interfacing unit which is slidably coupled tothe shuttle-support unit. Mold-coupling members are provided forremovably coupling the first movable mold platen unit and the secondmovable mold platen unit to the shuttle-mold interfacing unit.

During operation of the shuttle assembly, a shuttle-drive unitselectively shuttles the shuttle-mold interfacing unit in a preferablyhorizontal shuttle-travel path between: (i) a first shuttle position atwhich the first movable mold platen unit, when coupled thereto, issituated at a first unloading/loading position, and the second movableplaten unit, when coupled thereto, is situated at a clamping position;and (ii) a second shuttle position at which the first movable moldplaten unit, when coupled thereto, is situated at the clamping position,and the second movable platen unit, when coupled thereto, is situated ata second unloading/loading position. In the preferred embodiment, thefirst and the second movable platen units are loaded/unloaded onopposite sides of the clamping position.

A control system is also provided for automatically and manuallycontrolling operation of the injection molding machine including, forexample, the shuttle assembly, supply assembly, extruder assembly,injection assembly and clamping assembly.

Other features and advantages of the present invention will becomeapparent from the following detailed description of the preferredembodiment made with reference to the accompanying drawings, which forma part of the specification.

BRIEF DESCRIPTION OF THE DRAWINGS

In the annexed drawings:

FIG. 1 is a schematic, perspective view of an injection molding machineaccording to the present invention, the machine including a shuttleassembly, a stock supply assembly, an extruder assembly, an injectionassembly, a mold pallet assembly, a clamping assembly and a controlsystem;

FIG. 2A-2L are schematic front elevations of the injection moldingmachine showing the components thereof in sequential stages of themolding process;

FIG. 3 is a generally isolated front view of the shuttle assembly;

FIG. 4 is a top plan view of the shuttle assembly;

FIG. 5 is a side isolated view of certain components of the shuttleassembly and the mold pallet assembly;

FIG. 6 is an exploded perspective view of certain components of theshuttle assembly and the mold pallet assembly;

FIG. 7 is a top view of the movable clamping device; and,

FIG. 8 is a side view of a portion of the clamping assembly, namely amovable clamping device, this device being shown generally isolated fromthe other components of the machine.

DETAILED DESCRIPTION

Referring now to the drawings in detail, and initially to FIG. 1, aninjection molding machine according to the present invention isindicated generally at 20. The injection molding machine 20 includes ashuttle assembly, indicated generally at 22, which allowsunloading/loading steps to be performed on one movable mold platen unitwhile another movable mold platen unit is participating in the moldingprocess.

The outer structure of the injection molding machine 20 comprises aframe 24 which includes two vertical side plates 25, a top horizontalmounting plate 26, a horizontal injector plate 27 and a horizontal baseplate 28. The horizontal plates 26-28 extend between and support thevertical plates 25 to rigidify the machine frame 24. The side plates 25have C-shaped cutouts 30 formed thereon which cooperatively define amolding chamber, indicated generally at 33. As shown in FIG. 1, theshuttle assembly 22 is mounted on frame 24 and extends horizontallythrough the molding chamber 33.

The operational components of the injection molding machine 20 aredesigned to convert stock material into molded products, such as a firstmolded product M and a second molded product MP (not specifically shownin FIG. 1). The operational components include a stock supply assembly(not specifically shown), an extruder assembly comprising a conventionalscrew extruder, indicated generally at 36, and an injection assemblyincluding a conventional nozzle unit and hydraulic cylinder, indicatedgenerally at 38. These assemblies may be of a conventional constructionand thus their particular structure and operation will not be expandedon in detail in this discussion. The injection machine or injectionpress of the illustrated embodiment is a 25 ton injection press of thetype manufactured by Sanyu of Japan.

The operational components of the injection molding machine 20 furtherinclude a mold pallet assembly, indicated generally at 40, and aclamping assembly indicated generally at 42. The mold pallet assembly 40includes: a stationary upper mold platen unit, indicated generally at50, a first-movable lower platen unit, indicated generally at 52, and asecond movable lower mold platen unit, indicated generally at 54. Theclamping assembly 42 includes a stationary upper clamping plate,indicated generally at 56, and a movable lower clamping device,indicated generally at 58. The stationary clamping plate 56 is an upperbolster plate secured between the vertical side plates by conventionalfasteners.

While some of the features of the mold pallet assembly 40 and theclamping assembly 42 are of a conventional construction and part of aconventional Sanyu press, these assemblies coordinate with the shuttleassembly 22. The specific "shuttle-coordinating" features of the moldpallet assembly 40 and the clamping assembly 42 are discussed in detailbelow.

In a typical operational sequence of the injection molding machine 20,the stock supply assembly supplies a certain amount of stock materialthrough an opening (not specifically shown) in the extruder assembly 36.The extruder assembly 36 plasticizes the stock material into aninjection material which is then conveyed to the injection assembly 38.The shuttle assembly 22 and the clamping assembly 42 cooperate tomanipulate the various components of the mold pallet assembly 40 to forma complete mold cavity to receive the injection material from theinjection assembly 38.

The manipulation of the mold pallet assembly 40 particularly includesthe shuttle assembly 22 shuttling the movable mold platen units 52 and54 in a shuttle-travel path between a clamping position and first andsecond loading/unloading positions, respectively. Additionally, thelower clamping device 58 moves the movable mold platen unit 52 or 54 inalignment therewith in a clamp-travel path between a shuttling level andan injection level. Preferably, the shuttle-travel path is in asubstantially horizontal direction and the clamp-travel path is asubstantially vertical direction.

The particular movement of the movable mold platen units 52 and 54during the molding operation are best explained by referring toschematic FIGS. 2A-2J. For ease in explanation, the arrangement shown inFIG. 2A may be designated as a starting point, and at this point, thecomponents of the machine are arranged as follows:

i) the stationary mold platen unit 50 is secured to the clamping plate56, which is attached to the machine frame 24 intermediate the verticalplates 25;

ii) the movable mold platen units 52 and 54 are releasably coupled tothe shuttle assembly 22 whereby they are both situated at the shuttlinglevel;

iii) the first lower movable mold platen unit 52 is situated in aclamping position which is vertically aligned with but spaced from thestationary upper mold platen unit 50;

iv) the second movable mold platen unit 54 is situated in a secondloading/unloading position which is offset to the right from thestationary mold platen unit 50 as viewed in FIG. 2A; and

v) the movable clamping device 58 is coupled to the first movable lowermold platen unit 52.

In the next stage of the molding operation, the movable clamping device58 is moved upward from the shuttling level whereby the first movablelower mold platen unit 52 is uncoupled from the shuttle assembly 22.(See FIG. 2B). This movement is continued until the movable clampingdevice 58 reaches an injection level at which the first movable lowermold platen unit 52 will be joined together with the stationary uppermold platen unit 50 to cooperatively form a first mold cavity 28. (SeeFIG. 2C). Once the first mold cavity 28 has been formed, the moldingprocess may begin. Simultaneously, unloading/loading duties may bepreformed on the second movable mold platen unit 54 which is situated inthe second loading/unloading position.

After the molding process is completed, the movable clamping device 58is retracted to vertically lower the first movable platen unit 52 fromthe injection level to the shuttle level, whereby it is re-coupled tothe shuttle assembly 22. (See FIGS. 2D and 2E). The shuttle assembly 22will then horizontally index the first movable mold platen unit 52 fromthe clamping position to the first unloading position, with suchhorizontal motion being operative to uncouple the first mold platen unitfrom the piston rod of the movable lower clamping device 58. Thishorizontal shuttling of the first movable mold platen unit 52 willsimultaneously result in the second movable mold platen unit 54 beinghorizontally moved from the second loading/unloading position to theclamping position. Such horizontal movement will also result in thesecond movable platen being coupled to the piston rod of movableclamping device 58. (See FIGS. 2F and 2G).

Once the first movable mold platen unit 52 is returned to the firstunloading/loading position, unloading and loading duties are performedthereon in an easily accessible location. Simultaneously the piston rodof movable clamping device 58 is moved upward to elevate the secondmovable mold platen unit 54 and uncouple it from the shuttle assembly22. (See FIG. 2H). The upward movement of the movable clamping device 58will continue until the second movable mold platen unit 54 reaches theinjection level. At the injection level the platen unit 54 is joinedtogether with the stationary mold platen unit 50 to cooperatively form asecond mold cavity 29. (See FIG. 2I). A shot of injection material isthen injected into the second mold cavity to create a second moldedproduct MP.

Once the second molded product MP has been made, the movable clampingdevice 58 is retracted to lower the second movable mold platen unit 54from the injection level to the shuttle level, whereby the second unit54 is re-coupled to the shuttle assembly 22. (See FIGS. 2J and 2K). Theshuttle assembly 22 subsequently horizontally moves the second movablemold platen unit 54 from the clamping position to the secondunloading/loading position. This horizontal movement thereby uncouplesthe second mold platen unit 54 from the piston rod of the movableclamping device 58 and simultaneously horizontally moves the firstmovable mold platen unit 52 to the clamping position. (See FIG. 2L).

The second molded product MP may then be unloaded from the secondmovable mold platen unit 54 and another unfinished product may besubsequently loaded therein. At this point in the cycle, the machine 20has returned to the "starting point" of FIG. 2A and the cycle may becontinuously repeated until the desired number of molded products M, MPhave been produced.

Referring now to FIGS. 3-4, the shuttle assembly 22 includes ashuttle-support unit, indicated generally at 70. The shuttle supportunit 70 comprises a pair of parallel tracks 72 and end plates 73 and 74attached to opposite ends thereof. The shuttle-support unit 70 issecured to the machine frame 24 by a pair of support blocks 75 which areroughly T-shaped in transverse geometry. (See FIG. 3). The tracks 72extend horizontally through, and beyond each side of, the moldingchamber 33.

A shuttle-mold interfacing unit or table, indicated generally at 76, isslidably coupled to and supported by the tracks 72 and its motionrelative thereto is controlled by a shuttle-drive unit 78. In certainstages of the molding process, the movable mold platen units 52 and 54are securely, but removably, coupled to the shuttle-mold interfacingunit 76. The shuttle components are designed so that shuttle-moldinterfacing unit 76 may be selectively reciprocally indexed in ashuttling-travel path between a first loading/unloading position and asecond loading/unloading position as discussed above and shown in FIGS.2A-K.

The coupling of the shuttle-mold interfacing unit 76 to the tracks 72 isaccomplished by linear-motion coupling members 84 which are carried byand extend downwardly from unit 76 as best seen in FIG. 5."Linear-motion coupling member" in this context corresponds to any typeof coupling component, such as conventional bearings, which would allowlinear movement of the unit 76 relative to the tracks 72. In theillustrated embodiment of FIG. 5, the coupling members 84 each include adownwardly opening channel and bearings 90. Stops 100 are additionallyprovided secured to the end plates 73, 74 as illustrated in FIGS. 3 and4. The stops 100 are provided to engage the unit 76 and are preferablyconventional spring shock absorbers.

The shuttle-drive unit 78 includes a conventional hydraulic cylinder 92having a shuttle piston rod 94 which is attached on one end to acylinder-support bracket 96 secured to the first end plate 73 of theshuttle-support unit 70. A rod-interface bracket 98 secures the secondend of the cylinder 92 to an intermediate portion of the shuttle-moldinterfacing unit 76. In FIG. 4 the shuttle piston rod 94 is fullyextended relative to the cylinder 92 and the length of its stroke issuch that in this fully extended condition, the shuttle-mold interfacingunit 76 is located in the second loading/unloading position. The lengthof the stroke of the shuttle-drive unit 78 is also chosen so that whenthe shuttle-rod 94 is fully retracted, the shuttle-mold interfacing unit76 will be located in the first loading/unloading position.

As best shown in FIGS. 4 and 6, the shuttle-mold interfacing unit 76 isrectangular and includes first and second octagonal openings 120, 122which respectively correspond to the coupling location of the first andsecond movable lower mold platen units 52 and 54, respectively. Theshuttle-mold interfacing unit 76 additionally includes a first set ofpilot openings 124, and a second set of pilot openings 125, each of saidopenings having bearings 124a, 125a for engagement with coupling posts.Openings 126, openings 127 are also provided in the interfacing unit forengagement with fasteners securing the linear coupling members 84 inposition. (See FIG. 6).

As was indicated above, the mold pallet assembly 40 includes astationary mold platen unit 50, a first movable mold platen unit 52, anda second movable mold platen unit 54. The upper mold platen unit 50preferably remains stationary throughout the molding process andincludes a mold profile plate which has a complimentary contour relativeto the mold profiles of the movable mold platen units 52 and 54.

The first and second movable mold platen units 52 and 54 are essentiallyidentical in construction. The first mold platen unit 52 includes afirst shuttle/clamp-interfacing plate 130, having a first set ofcoupling posts 132 and a first octagonal insert 133 secured thereto. Theoctagonal insert is secured to the plate via conventional fastenersthrough openings 131. The coupling posts 132 project from theshuttle/clamp interfacing plate 130 and are sized and arranged to beselectively inserted into the pilot openings 124 in the shuttle-moldinterfacing unit 76. The octagonal insert 133 also projects downwardlyfrom the mold-shuttle/clamp interfacing plate 130 and is sized andarranged to be inserted into the first octagonal opening 120 in theshuttle-mold interfacing unit 76. The first mold platen unit 52 alsoincludes a clamping-coordinating component, which is indicated generallyat 134, which is connected to and extends downwardly from octagonalinsert 133. The clamping-coordinating component 134 is selectivelycoupled to the lower clamping device 58 of the clamping assembly 42 aswill be described in more detail below.

The second movable mold platen unit 54 is essentially identical to thefirst movable mold platen unit 52, and includes a secondshuttle/clamp-interfacing plate 136, having a second set of couplingposts 138, a second octagonal insert 139, and a secondclamping-coordinating component 140. The insert 139 is secured to theplate 136 via conventional fasteners through openings 137.

The first movable mold platen unit 52 further includes a firstinsulation plate 142 and a first lower heating platen 144 which maintainthe necessary temperature conditions within the mold cavity 28 duringthe molding process. Heating elements 184 for engagement with a heaterunit are provided in the platen 144. The first insulation plate 142 isstacked on top of the first mold-shuttle/clamp-interfacing plate 130 andthe heating platen 144 is stacked on top of the first insulation plate142. The components are then fixedly attached in this arrangement byconventional fasteners 150 which extend through aligned openings 152,154, and 156.

The second movable mold platen unit 54 likewise includes a secondinsulation plate 162 and a second lower heating platen 164. The secondlower heating platen 164 maintains desired temperature conditions duringthe molding process using heating elements 187, which engage a heaterunit in the platen 164. These components 162 and 164 and the secondshuttle/clamp-interfacing plate 136 are stacked in a manner similar tothe comparable components of the first movable mold platen unit 52, andsecured together by conventional fasteners 170 which extend throughopenings 182, 183, and 186.

The shuttle assembly 22 includes a first heating unit 180 and a secondheating unit 182 which are thermally coupled to the first and secondheating platens 144, 164 and heating elements 184, 187, respectively(see FIGS. 3, 4 and 6). Coupling is accomplished by engagement of theelements 184, 187 in the first lower heating platen 144 and second lowerheating platen 164, respectively with the first heating unit 180 andsecond heating unit 182, respectively. When coupled in this manner asshown in FIG. 3, the first heater unit 180 extends in cantilever fashionfrom one end of the shuttle-mold interfacing unit 76. The second heatingunit 182 is coupled to the opposite end of the shuttle-mold interfacingunit 76 in a similar manner.

An electrical power source supplies the heating units 180 and 182 withpower via electrical supply lines (not specifically shown). The firstand second set of supply lines extend from terminal boxes 188 and 190,respectively, and are contained within first and second"extendable/retractable" umbilical conduits 192 and 194, respectively.As shown in FIG. 3, the first terminal box 188 is mounted on theshuttle-support unit 70 adjacent the first end plate 73, and the secondterminal box 190 is mounted adjacent the second end plate 74. Thismounting arrangement results in the conduits 192 and 194 extending inroughly J-shaped paths. The conduits 192 and 194 have sufficientflexibility and linear extension and contraction capacity to accommodatehorizontal shuttle movement and vertical mold platen unit movement.

As indicated above, the clamping assembly 42 includes an upperstationary clamping plate 56 and a lower movable clamping device 58. Thestationary clamping plate 56 illustrated in FIG. 1, is secured to theframe 24 intermediate the vertical plates 25 below the injector plate 27which in part supports the injection assembly 38. The movable clampingdevice 58 includes a clamp-mold interfacing unit indicated generally at202 and a clamp cylinder unit, indicated generally at 204. (See FIGS. 7and 8).

The clamp-mold interfacing unit 202 includes an octagonal base plate 206which is of a similar geometry, but lesser dimensions, than theoctagonal openings 120/122 in the shuttle-mold interfacing unit 76. Inthis manner, the clamp-mold interfacing unit 202 may pass between thetracks 72, and through the appropriate octagonal opening 120/122 in theshuttle-mold interfacing unit 76, to interface and move the movable moldplaten unit 52/54. The clamp-mold interfacing unit 202 further includesa clamp-mold coupling component 208 which coordinates with theclamping-coordinating components 134 and 140 of the movable mold platenunits 52 and 54, respectively.

The movable clamping device 58 is secured to the machine frame 24supported on a mounting plate 210 which is secured to the verticalplates 25 via conventional fasteners, as shown in FIG. 8. As set forthabove, the movable clamping device 58 includes a clamp cylinder unit 204having a conventional hydraulic cylinder 220 including a piston rod 222,a supporting base 212 and supporting rods 213. The clamp-moldinterfacing unit 202 includes a pair of guide posts 214 which projectdownwardly from the bottom surface of the octagonal base plate 206 andare slidably received in corresponding openings 216 in the mountingplate 210. The mounting plate 210 further includes a central opening orbore 218 which slidably receives the piston rod 222 of the clampcylinder unit 204. The bottom surface of the octagonal base plate 206 ofthe clamp-mold interfacing unit 202 is secured to the piston rod 222.

The clamp-mold coupling component 208 is generally T-shaped in crosssection, and has first and second legs 230, 232 in perpendicularrelationship to one another. A locating pin 234 extends from a centralportion of the second leg 232 and a pair of triangular detentes 236 arelocated on each side of the second leg 232. The T-shape of the couplingcomponent 208 allows it to be slidably received within an open-endedcross-shaped channel 240 in the clamping-coordinating component 134 or140. When properly positioned, the locating pin 234 will be insertedinto an opening 242 in the component 134/140 and ball plungers 244 maybe provided to engage the detentes 236. Thus, horizontal indexing of thelower platen units 52 and 54 will result in the coupling component 208at the free end of clamp piston rod 222 being received endwise withinthe clamp-mold coupling component 208 on the lower platen unit assuringthe clamping position.

One may now appreciate that the machine 20 is adapted to allow unloadingand loading steps to be performed on one movable mold platen unit 52/54while the other unit is participating in the injection/curingprocedures. Consequently, the machine 20 is not idle for any significantlength of time during the molding process. This reduction in idlemachine time results in increased productivity of both the machine 20and the operator. Additionally, because the first and second unloadingpositions are offset from the molding chamber 33, and are situated at asingle shuttling level, the operator may easily and efficiently performthe unloading and loading steps. Furthermore, the movable mold platenunits 52 and 54 may be easily initially installed on the shuttleassembly 22. Still further, the shuttle assembly 22 may be heldstationary in either the first or second unloading position and themachine 20 may be used in a "single" molding process.

In the preferred embodiment of the injection molding machine 20, acontrol system 60 is additionally provided, as illustrated in FIG. 1,which is programmable to control all aspects of operation of the supplyassembly, extruder assembly 36, injection assembly 38, shuttle assembly22, mold pallet assembly 40 and clamping assembly 42. The control systemincludes the main electric power supply (not illustrated) for themachine 20. Additionally, the control system includes an hydraulic unit61 which actuates the extruder assembly, injection assembly, shuttleassembly 22 and clamping assembly 42. The hydraulic unit is preferably aconventional closed loop flow and valve system. Pressure and temperaturesafety switches may also be provided in the machine 20 which interfacewith the control system 60.

The control system 60 includes a conventional programmable computer 62for programming the predetermined desired settings and operatingconditions for operation of the machine 20, and a control panel 63 foruse by an operator during operation of the machine. In the preferredembodiment, the control panel 63 is a Cincinnati Electrosystems 3045operator interface, and the programmable computer is a Mitsubishi ASeries logic controller. The computer and control panel provideprogrammed or manual instructions for all machine functions, includingactivation of the various cycles described above. While the specificcommercial systems listed are preferred, they may be any one of a numberof commercial operator-interface programmable systems. Additionally, theoperator control panel 63 includes a manual safety switch to enable theoperator to shut off the machine during any stage of operation.

Based on the information programmed into the control system 60, anautomatic cycle can be developed to operate the shuttle assembly 2.Alternatively, the operator controls can be used to initiate the machinecycles as may be desired.

Although the preferred form of the apparatus has been described above,it should be understood that obvious alterations may be made to thepresent disclosure to achieve comparable features and advantages. Withthe present disclosure in mind, it is believed that such features andadvantages will become apparent to those of ordinary skill in the art.

What is claimed is:
 1. An injection molding machine, comprising amachine frame, a mold pallet assembly, and a shuttle assembly;said moldpallet assembly including a stationary mold platen unit, a first movablemold platen unit, and a second movable mold platen unit; said stationarymold platen unit being fixedly secured to said machine frame; saidshuttle assembly including a stationary shuttle-support unit attached tosaid machine frame and a shuttle-mold interfacing unit which is slidablycoupled to said shuttle support unit and which is adapted to removablycouple said first movable mold platen unit and said second movable moldplaten unit to said shuttle assembly; said shuttle assembly furtherincluding a shuttle-drive unit operative to selectively index saidshuttle-mold interfacing unit in a shuttling-travel path between:a firstshuttle position whereat said first movable mold platen unit, whencoupled thereto, is situated at a first loading/unloading position andsaid second movable platen unit, when coupled thereto, is situated at aclamping position, and a second shuttle position whereat said firstmovable mold platen unit, when coupled thereto, is situated at saidclamping position, and said second movable platen unit, when coupledthereto, is situated at a second loading/unloading position.
 2. Aninjection molding machine as set forth in claim 1 wherein said firstloading/unloading position is offset to one side of said clampingposition and said second loading/unloading position is offset to anopposite side of said clamping position.
 3. An injection molding machineas set forth in claim 1 further comprising a clamping assembly whichincludes a clamp-mold interfacing unit and a clamp-drive unit operativeto selectively move said clamp-mold interfacing unit in aclamping-travel path between a shuttling position and an injectionposition.
 4. An injection molding machine as set forth in claim 3wherein said shuttling-travel path is in a direction substantiallyperpendicular to the direction of said clamping-travel path.
 5. Aninjection molding machine as set forth in claim 4 wherein saidshuttling-travel path is in a substantially horizontal direction andwherein said clamping-travel path is in a substantially verticaldirection.
 6. An injection molding machine as set forth in claim 3wherein said shuttle-mold interfacing unit, said clamp-mold interfacingunit, said first movable mold platen unit, and said second movable moldplaten unit include components adapted to:couple said first movable moldplaten unit to said clamp-mold interfacing unit when said first moldplaten unit is coupled to said shuttle-mold interfacing unit and saidshuttle-mold interfacing unit is positioned in said second unloadingposition; uncouple said first movable mold platen unit from saidshuttle-mold interfacing unit when said clamp-mold interfacing unit ismoved from said shuttling position to said injection position; re-couplesaid first movable mold platen unit to said shuttle-mold interfacingunit when said clamp-mold interfacing unit is moved from said injectionposition to said shuttling position; uncouple said first movable moldplaten unit from said clamp-mold interfacing unit when said shuttle-moldinterfacing unit is moved from said second-unloading position to saidfirst unloading position; couple said second movable mold platen unit tosaid clamp-mold interfacing unit when said second mold platen unit iscoupled to said shuttle-mold interfacing unit and said shuttle-moldinterfacing unit is positioned in said first unloading position;uncouple said second movable mold platen unit from said shuttle-moldinterfacing unit when said clamp-mold interfacing unit is moved fromsaid shuttle position to said injection position; re-couple said secondmovable mold platen unit to said shuttle-mold interfacing unit when saidclamp-mold interfacing unit when said clamp-mold interfacing unit ismoved from said injection position to said injection position; anduncouple said second movable mold platen unit from said clamp-moldinterfacing unit when said shuttle-mold interfacing unit is moved fromsaid first unloading position to said second unloading position.
 7. Aninjection molding machine as set forth in claim 1 wherein saidshuttle-support unit includes a pair of parallel tracks and alinear-motion coupling member which slidably couples said shuttle-moldinterfacing unit to said pair of parallel tracks.
 8. An injectionmolding machine as set forth in claim 1 wherein said first movable moldplaten unit is essentially identical in size and shape to said secondmovable mold platen unit.
 9. A shuttling assembly for an injectionmolding machine having a machine frame and a mold pallet assembly whichincludes a first movable mold platen unit and a second movable moldplaten unit; said shuttle assembly comprising:a shuttle-support unitadapted to be attached to the machine frame; a shuttle-mold interfacingunit, slidably coupled to said support unit; mold-coupling members forremovably coupling the first movable mold platen unit and the secondmold platen unit to said shuttle-mold interfacing unit; a shuttle-driveunit operative to selectively reciprocally index said shuttle-moldinterfacing unit in a shuttle-travel path between:a first shuttleposition whereat the first movable mold platen unit, when coupledthereto, is situated at a first unloading position, and the secondmovable platen unit, when coupled thereto, is situated at a clampingposition, and a second shuttle position whereat the first movable moldplaten unit, when coupled thereto, is situated at the clamping position,and the second movable platen unit, when coupled thereto, is situated ata second unloading position.
 10. A shuttling assembly as set forth inclaim 9 wherein said shuttling-travel path is in a substantiallyhorizontal direction.
 11. A shuttling assembly as set forth in claim 10wherein said shuttle support unit includes a pair of parallel tracks anda set of linear-motion coupling members which slidably couple saidshuttle-mold interfacing unit to said pair of parallel tracks.
 12. Aninjection molding machine comprising:a stationary upper mold platenunit, first and second lower mold platen units adapted to be removablycoupled in spaced relationship to a shuttle, a drive to reciprocallyindex the shuttle between first and second positions, and a clampingmechanism selectively to elevate either the first or second lower moldplaten unit in alignment therewith from the shuttle into matingrelationship with the upper mold platen unit while the other lowerplaten unit is unloaded and/or loaded.